References of "Habraken, Anne"
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See detailIdentification of hardening behavior using inverse modeling and image correlation
Lecompte, D.; Cooreman, S.; Sol, H. et al

in Proceedings of the SEM annual conference and exposition 2006 (2006)

The basic principle of an inverse modeling procedure as it is used for parameter identification, is the generation of a complex and heterogeneous deformation field that contains as much information as ... [more ▼]

The basic principle of an inverse modeling procedure as it is used for parameter identification, is the generation of a complex and heterogeneous deformation field that contains as much information as possible about the parameters to be identified. One way of obtaining such a non-homogeneous deformation is by making the geometry of the specimen less regular. Another possibility is to make the loading conditions more complex. In this paper both options are actually combined by using a biaxial tensile test on a cruciform specimen in order to identify the parameters of a Swift isotropic hardening law. The yield criterion is modeled by the isotropic Von Mises criterion. The optimization technique used is a constrained gradient based Newton-type routine, which means that in every iteration step, a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be optimized. The functional to be minimized is a least-squares expression of the discrepancy between the measured and the simulated strain fields at a certain load. The numerical routines as well as the identification results, based on simulated strain fields, are discussed. [less ▲]

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See detailA phenomenological model to simulate mechanical tests on ultrafine-grained aluminium produced by ECAE
Diouf, Boubakar; El Houdaigui, Fouad; Poortmans, S. et al

in Mota Soares, C. A. (Ed.) Proceedings of the III European Conference on Computational Mechanics Solids (ECCM III) (2006)

Results of FEM simulations predicting the mechanical behavior at room temperature of test specimens of ultrafine-grained aluminum produced by ECAE are presented. The constitutive law is either based on a ... [more ▼]

Results of FEM simulations predicting the mechanical behavior at room temperature of test specimens of ultrafine-grained aluminum produced by ECAE are presented. The constitutive law is either based on a Hill model or on the Minty micro-macro model and coupled with an isotropic hardening law and/or kinematic hardening law. The yield locus shape, its size and its position during tension, compression and torsion tests have been studied. Initial texture measurements allow the identification of a constitutive law based on a set of representative crystals and crystal plasticity approach using a Full- Constraint Taylor model. Finite element simulations using the previous constitutive laws are compared with experimental investigations. The results show that applying an initial back stress identified by tensile and compression tests to the yield locus predicts the initial flow stress in torsion test. The Minty micro-macro model coupled with a Voce type hardening model gives a good agreement with experimental results for the prediction of the shape at different stages of deformation of a compressed test specimen. The simulation of tensile tests underline the need of inverse modeling as, due to the test specimen shape, the test is far from being homogeneous. The link between test specimen length and the necking appearance is studied. [less ▲]

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See detailAn FEM-aided investigation of the deformation during single point incremental forming
He, S.; Van Bael, A.; Van Houtte, P. et al

in Modelling & Simulation in Materials Science & Engineering (2006)

Incremental forming is an innovative and flexible sheet metal forming technology for small batch production and prototyping, which does not require any dedicated die or punch to form a complex shape. This ... [more ▼]

Incremental forming is an innovative and flexible sheet metal forming technology for small batch production and prototyping, which does not require any dedicated die or punch to form a complex shape. This paper investigates the process of single point incremental forming of an aluminium cone both experimentally and numerically. Finite element models are established to simulate the process. The output of the simulation is given in terms of final geometry, the thickness profile of the product and the strain history and distribution during the deformation. Comparison between the simulation results and the experimental data is made. [less ▲]

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See detailFast method to predict an earing profile based on Lankford coefficients and yield locus
Lelotte, Thomas; Duchene, Laurent ULg; Habraken, Anne ULg

in Mota Soares, C. A. (Ed.) Proceedings of the III European Conference on Computational Mechanics Solids (ECCM III) (2006)

This paper compares three methods to determine the earing profile that appears during the deep-drawing test of a circular steel sheet. Three steel grades will be studied. The first method is an ... [more ▼]

This paper compares three methods to determine the earing profile that appears during the deep-drawing test of a circular steel sheet. Three steel grades will be studied. The first method is an experimental test made by a hydraulic press. The second one is a finite ele-ment method (FEM) deep-drawing simulation using a micro-macro texture based constitutive law. The last one directly determines the general aspect of the earing profile from the yield locus which is computed from the initial texture. The goal of this study is to validate the last approach. So, an earing profile prediction can quickly be obtained just from material’s tex-ture. [less ▲]

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See detailDevelopment and performance assessment of an improved 8-node mixed type FEM element
Duchene, Laurent ULg; de Montleau, P.; Habraken, Anne ULg

in Juster, Neal; Rosochowski, Andrzej (Eds.) Proceedings of the 9th International ESAFORM Conference on Material Forming (2006)

Several finite element (FE) simulations were investigated using a recently developed mixed type element: the BWD3D. The main formulation of the element is largely described, with particular focus on the ... [more ▼]

Several finite element (FE) simulations were investigated using a recently developed mixed type element: the BWD3D. The main formulation of the element is largely described, with particular focus on the shear locking treatment. The formulation of the former BLZ3D element is also presented for comparison. The examples investigated in the present study were beam bending, large strain torsion, incremental forming and deep drawing .The numerical results obtained with both elements were compared to experiments. [less ▲]

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See detailCharacterization of Duplex steel Uranus 76N during deformation and heat treatment
Lecomte-Beckers, Jacqueline ULg; Moureaux, P.; Carton, Marc ULg et al

in Physica Status Solidi A. Applications and Materials Science (2006), 203(15), 3651-3664

Duplex Uranus 76N is characterized by metallography, thermal and mechanical analysis. The investigation shows that the microstructure of such a Duplex strongly depends on the cooling conditions ... [more ▼]

Duplex Uranus 76N is characterized by metallography, thermal and mechanical analysis. The investigation shows that the microstructure of such a Duplex strongly depends on the cooling conditions determining the quantity of austenite formed in the ferrite matrix. Numerical simulations of 76N behavior during the rolling process and service life require the knowledge of the recrystallization state during rolling steps at high temperature, thermal parameters such as dilatation, density, specific heat, thermal diffusivity, thermal conductivity and mechanical constitutive laws. These material parameters are determined and presented in this study. [less ▲]

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See detailQuality assessment of speckle patterns for digital image correlation
Lecompte, D.; Smits, A.; Bossuyt, Sven et al

in Optics & Lasers in Engineering (2006), 44(11), 1132-1145

Digital image correlation (DIC) is an optical–numerical full-field displacement measuring technique, which is nowadays widely used in the domain of experimental mechanics. The technique is based on a ... [more ▼]

Digital image correlation (DIC) is an optical–numerical full-field displacement measuring technique, which is nowadays widely used in the domain of experimental mechanics. The technique is based on a comparison between pictures taken during loading of an object. For an optimal use of the method, the object of interest has to be covered with painted speckles. In the present paper, a comparison is made between three different speckle patterns originated by the same reference speckle pattern. A method is presented for the determination of the speckle size distribution of the speckle patterns, using image morphology. The images of the speckle patterns are numerically deformed based on a finite element simulation. Subsequently, the displacements are measured with DIC-software and compared to the imposed ones. It is shown that the size of the speckles combined with the size of the used pixel subset clearly influences the accuracy of the measured displacements. [less ▲]

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See detailA 2.5 D finite element model for bending and straightening in continuous casting of steel slabs
Pascon, Frédéric ULg; Cescotto, Serge ULg; Habraken, Anne ULg

in International Journal for Numerical Methods in Engineering (2006), (68), 125-149

This paper presents a bi-dimensional slice model of the continuous casting process developed to focus on the risk of transverse cracking during bending and straightening of steel slabs. The model is based ... [more ▼]

This paper presents a bi-dimensional slice model of the continuous casting process developed to focus on the risk of transverse cracking during bending and straightening of steel slabs. The model is based on the finite element method and it integrates both thermal and mechanical aspects: temperature evolution, solidification, stress and strain developments. Generalized plain strain conditions are applied in the casting direction, allowing taking account of the extraction force applied to the slab as well as strains in this direction. The model also includes an original solution to counteract the generally wrong modelling of slab bulging with such slice models. The model has been applied to an industrial case of slab casting. Some numerical results illustrate the accuracy of the model compared to results of other models, measurements and observations on the caster. Transverse cracks are predicted to be the most likely to occur at the edge on the upper face, at the end of straightening of the slab. This is due to the combination of low ductility of the material with tensile stress and elongation in the casting direction in the straightening zone. This conclusion has been confirmed by the examination of slabs that present transverse cracks. [less ▲]

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See detailCaracterizacion del comportamiento elasto-plastico de placas metalicas
Flores, Paulo; Habraken, Anne ULg

(2006)

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See detailEffect of FEM choices in the modelling of incremental forming of aluminium sheets
He, S.; Van Bael, A.; Van Houtte, P. et al

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (2005)

This paper investigates the process of single point incremental forming of an aluminium cone with a 50-degree wall angle. Finite element (FE) models are established to simulate the process. Different FE ... [more ▼]

This paper investigates the process of single point incremental forming of an aluminium cone with a 50-degree wall angle. Finite element (FE) models are established to simulate the process. Different FE packages have been used. Various aspects associated with the numerical choices as well as the material and process parameters have been studied. The final geometry and the reaction forces are presented as the results of the simulations. Comparison between the simulation results and the experimental data is also made. [less ▲]

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See detailModelling of semi-continuous casting of cupro-nickel alloys
Pascon, Frédéric ULg; Pecquet, Etienne ULg; Zhang, Lihong ULg et al

in Papadrakakis, M.; Onate, E.; Schrefler, B. (Eds.) Proceedings of the International Conference on Computational Methods for Coupled Problems in Science and Engineering (2005)

This research developed at University of Liege aims to optimize the complete semi-continuous casting process at LBP Company, a producer of copper-nickel alloys (or cupro-nickels). The process consists in ... [more ▼]

This research developed at University of Liege aims to optimize the complete semi-continuous casting process at LBP Company, a producer of copper-nickel alloys (or cupro-nickels). The process consists in vertical casting of 7m long ingots. Some problems recurrently occur during casting process: formation of oscillations (wave length of about 500 mm), unsuitable concave cross-sections or internal cracks. In order to reduce the occurrence of such defects and to better understand their formation, we have been asked to develop a finite element model. The research focuses on two main topics: identification of material properties through laboratory tests and literature survey and the development of the numerical tool. The laboratory tests provide thermal and mechanical properties of the ingot and the mould, as well as heat transfer coefficients between the ingot and its surroundings (mould, air and water). These parameters are required for the numerical simulations of the process. In the second part of the research, numerical calculations have been performed using finite element method. Two types of 2D models have already been studied: horizontal slice and vertical slice. This first choice has been guided by the high coupling between thermal and mechanical aspects of the problem, leading to highly complex systems of equations and subsequent long CPU times. However, due to the limitations of such 2D models, a 3D formulation has then been considered and it is still in progress. [less ▲]

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See detailExperimental validation of the finite element simulation of the first stroke in single point incremental forming
Watzeels, Ken; Tunckol, Y.; Henrard, Christophe ULg et al

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (2005)

Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained particular interest in rapid prototyping and small volume production. The study of the underlying forming ... [more ▼]

Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained particular interest in rapid prototyping and small volume production. The study of the underlying forming mechanisms is supported by new developments in finite element simulations and experimental full field strain measurements. This article aims to describe the possibilities and difficulties encountered during validation of finite element predictions of the incremental forming process. The drawing of a straight line into a metal plate was selected as a first test case for this kind of validation. Results of both finite element simulation and experimental work will be discussed. [less ▲]

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See detailDevelopment of a contact model adapted to incremental forming
Henrard, Christophe ULg; Bouffioux, Chantal ULg; Godinas, A. et al

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (2005)

The objective of this article is to present the development of a new method for taking into account the contact between the tool and the blank during incremental forming. First, the need for such a model ... [more ▼]

The objective of this article is to present the development of a new method for taking into account the contact between the tool and the blank during incremental forming. First, the need for such a model is justified. Then, the basic features of the adapted dynamic explicit scheme are presented, followed by the new algorithms proposed and their programming. Finally, some conclusions and perspectives are drawn. [less ▲]

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See detailAxes rotation during simple shear test: Measurement and predictions
Lelotte, Thomas; Gerday, Anne-Françoise ULg; Flores, Paulo et al

in Oñate, E.; Owen, D. R. J. (Eds.) Proceedings of the VIII International Conference on Computational Plasticity (COMPLAS VIII) (2005)

For a simple shear test, the finite element (FE) local frame, that stays orthogonal, does not follow the anisotropic material frame. To study this effect, FE simulations have been compared with ... [more ▼]

For a simple shear test, the finite element (FE) local frame, that stays orthogonal, does not follow the anisotropic material frame. To study this effect, FE simulations have been compared with experimental results (optical and texture measurements) and it was shown that it is necessary to take into account the effect of texture updating for local axes rotation. [less ▲]

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See detailModeling of the fatigue cracks in welded beam-to-column connection of steel moment frame buildings submitted to earthquake
Lequesne, Cédric ULg; Gerday, Anne-Françoise ULg; Plumier, André ULg et al

in Aliabadi, M. H.; Planas, J.; Buchholz, F.-G. (Eds.) et al Proceedings of the 4th International Conference on Fracture and Damage Mechanics (2005)

Fatigue cracks in welded connections of steel moment frame buildings submitted to earthquakes are studied. The connections of beams with thick flanges designed to resist to seismic phenomena by plastic ... [more ▼]

Fatigue cracks in welded connections of steel moment frame buildings submitted to earthquakes are studied. The connections of beams with thick flanges designed to resist to seismic phenomena by plastic dissipation are presented. The structural components, the materials and the crack mechanics are described. To predict the crack initiation, the knowledge of residual internal stresses, generated by the welding process, is required. So these stresses are assessed by a FEM thermo-mechanical analysis. The potential sites of crack locations are detected by using an FEM model of the connection with the continuum damage model of Lemaître and Chaboche. After these FEM analyses, new meshes with specific elements located at the potential crack locations are defined. A cohesive zone law is used to model the crack propagation. This model describes the crack growth by analyzing the energy released by the generation of the new surfaces and damage micro-phenomena behind the crack tip. A constitutive tension-separation law computes this energy. In these cases of low cycle fatigue, the damage and the cyclic loading conditions are taken into account. [less ▲]

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See detailModélisation de la fissuration par fatigue des connexions poutres-colonnes de grands bâtiments en armature en acier lors de tremblements de terre
Lequesne, Cédric ULg; Plumier, André ULg; Habraken, Anne ULg

in Proceedings of the XVIIème congrès français de mécanique (CFM 2005) (2005)

Many steel frame buildings have cracked in beam-to-column connections during earthquakes. To determine the place and the moment of the crack initiation, a model of continuous damage is used in a finite ... [more ▼]

Many steel frame buildings have cracked in beam-to-column connections during earthquakes. To determine the place and the moment of the crack initiation, a model of continuous damage is used in a finite element computation. Cohesive zones model predicts the propagation. The residual stresses are evaluated before. [less ▲]

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See detailIdentification of elastic orthotropic material parameters by inverse modeling using ESPI
Lecompte, D.; Sol, H.; Vantomme, J. et al

in Proceedings of the 2005 SEM Annual Conference & Exposition on Experimental and Applied Mechanics (2005)

Parameter identification methods, which integrate optimization techniques and numerical methods such as the finite element method (FEM), offer an alternative tool for material characterisation. The most ... [more ▼]

Parameter identification methods, which integrate optimization techniques and numerical methods such as the finite element method (FEM), offer an alternative tool for material characterisation. The most common approach is to determine the optimal estimates of the model parameters by minimizing a selected measure-of-fit between the responses of the system and the model. The possibility is studied of retrieving the four independent elastic engineering constants for an orthotropic medium, based on the measurement of a heterogeneous displacement field. In the present case a tensile test is performed on a perforated specimen. The responses of the system, i.e. the surface displacements are measured with an Electronic Speckle Pattern Interferometer. Strains are subsequently calculated, based on the measured displacement field. A finite element model of the perforated specimen is made. The difference between the experimental and numerical strains is minimized in a least squares sense by updating the values of the parameters. The obtained material (or model) parameters are very well in agreement with the traditionally determined ones. [less ▲]

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See detailMaterial Identification Using a Bi-Axial Test Machine
Flores, Paulo; Moureaux, Pierre; Habraken, Anne ULg

in Proceedings of the International Conference on Advances in Experimental Mechanics (2005)

This paper shows the identification of material parameters for a DC06 IF steel sheet of 0.8 mm by mechanical tests. The experimental equipment used consists of a tensile test machine, a bi-axial test ... [more ▼]

This paper shows the identification of material parameters for a DC06 IF steel sheet of 0.8 mm by mechanical tests. The experimental equipment used consists of a tensile test machine, a bi-axial test machine able to perform plane-strain and simple shear tests separately or simultaneously and an optical strain gauge. Tensile, plane-strain and simple shear tests were performed at 0°, 45° and 90° from the sheet rolling direction in order to identify Hill 1948 and Hosford 1979 yield criteria. Two identification methods are used: one based on strain measurements (anistropy coefficients) and the other one based on stress measurements (plastic contours). The results confirm that mechanical tests applying other stress-states than tensile are required to obtain accurate material parameters identification. [less ▲]

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See detailIdentification of the parameters of a damage constitutive law for steel at elevated temperature
Castagne, S.; Habraken, Anne ULg

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (2005)

This paper presents the methodology and the results of the calibration of an interface damage law using experimental damage analyses and associated finite element simulations. The experimental damage ... [more ▼]

This paper presents the methodology and the results of the calibration of an interface damage law using experimental damage analyses and associated finite element simulations. The experimental damage analyses consist in acoustic tests realised on steel samples in order to determine the apparition of the first crack during compression. Finite elements simulations of these experiments allow the determination of the damage parameters using a reverse method. [less ▲]

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See detailDevelopment of a neural network to predict the final geometry of forged rings after cooling
Casotto, S.; Bruschi, S.; Pascon, Frédéric ULg et al

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (Vol. 2) (2005)

The paper deals with an application of Artificial Neural Networks (ANNs) to predict the geometry of hot forged pieces after cooling. Different ANNs have been considered and evaluated; then a network with ... [more ▼]

The paper deals with an application of Artificial Neural Networks (ANNs) to predict the geometry of hot forged pieces after cooling. Different ANNs have been considered and evaluated; then a network with two hidden layers has been set up. Training and testing data have been obtained through calibrated numerical simulations of the cooling phase carried out with a finite element (F.E.) code. The good agreement between predicted and numerical results confirms the possibility of using well-trained neural network to foresee final dimensions of pieces after hot forging operations. [less ▲]

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